wont idle... hardly running... no power...

[Broncobowsher]

On a duel plane intake the drivers side of carb feeds fuel to the 2 3 5 8 cylinders. The passenger side of carb feeds fuel to the 1 4 6 7 cylinders. If this help's anyone, but check the plug's no fuel on them = fuel problem. Fuel on the plug's = firing problem.

Saved me the typing. That is exactly what it look like to me as well.
Carb problem is about the only thing it could be.

 

[1971BroncoSport]

There was an earlier question about vacuum leaks. If you took apart all the vacuum line connections and those that were likely capped off - did you get them all back together? Do you hearing any hissing - that would be a telltale sign. If you do figure out which port it is - put a finger over it while the engine is running and see if it improves.

 

[broncobilly72]

Got a timing light? If you do you can use it to check spark to each cylinder. Are your plug wires in the correct firing order? Could be that your dizzy is off 180 degrees. Last but not least I had the same problem and found out that my camshaft had broken in the center.....went from a V8 to a V4 in an instant!

 

[YNOTBOB2007]

How do I check spark to each cylinder with a timing light? I have a digital light. Thanks.

 

[Bronco717274]

Hook your light to battery, connect the one that hooks to plug wire up and spin it over while holding the triger on timig light if light blinks off and on its firing. Move on to the next wire and repeat until you have done all 8 wires.

 

[YNOTBOB2007]

When you say spin it over, do you mean spin the clamp around the wire 360 degrees? And does it matter what the timing light is set for as far as the blinking goes? If my light is set for 8 degrees for timing, and no change to blinking when I spin the clamp around the wire, then the wire is good? Thanks. Good test to check wires and plugs.

 

[Broncobowsher]

I don't know why there is such a fixation on the ignition system when it clearly shows itself to be a fuel problem?

Want something funny? Take the carb off and install it backwards. Linkage won't hook up (do it by hand) and you may need a longer rubber fuel line. But the other 4 cylinders will suddenly not be working and the 4 dead ones will suddenly work just fine.

 

[bad 68]

Any chance there was a rag shoved in the intake below the carb?

 

[Bronco717274]

On the spinning over I meant crank the engine over a few times to see if the light blinks. Do that on every one, but I still think its in your carb, did you use new gaskets when you put your intake back on?? If not that might be your problem. But as I stated before it's missing on the drivers side of the carb I don't think you have a dist.problem. Wish I was closer I could just show you.

 

[twisted77]

Something tells me the Idle air mix screw on that bank is now GONE. Maybe fell out in that last 1 1/2 mile trip.

Bryce

 

[lman]

Well found out that the problem was the module inside the dist. Replaced that and it runs fine. Coil might be overheating after a while of running though.

 

[jonpblewis@yaho]

I just had a problem with my Malory Unilight dizzy. A screw on one side of the sensor came out and allowed the lose sensor to move around and that pulled the wires into the dizzy witch then got cut up by the roter. I patched up the wires but It hardly ran like it was not firing on all or missing and then died. Something had gone wrong with the sensor. I had my old dizzy with points to swap it out till I got a new electronic sensor. With the Malory Unilight You have to be sure it is powered correctly. Check that there is a resistor in/before the coil or a resistor wire from the ignition to the coil. I also disconnected the 12 volt to the coil from the starter relay. You can't let too much go to it or it will fail. $100 + for a new one so Down load the wiring diagram and installation instructions from Malory make sure you have it right.

I win !!!
Glad you got it figured Dude.
I knew from your discription and what mine did when it died that that was probably it. Did you check to make sure that the power to the coil is correct? You don't want to burn out another one.

 

[Bronco717274]

Well I'll be the first to admit I was wrong, but just from your discription I would have sworn it was in the carb. Congrats on getting it going.

 

[twisted77]

And you only had 4 cly not fireing? The same 4 all the time. Hmmm

 

[jonpblewis@yaho]

I'm not sure how the Malory sensor works but I think it can fail in a way that would have it only firing on select cyls? Its an optical sensor. I'm curious about how it functions now. dose anyone know? I'll see if I can find some info about it. They cost a lot so they might have more going on in them than we might think.

 

[twisted77]

he is running points. To be honest Mallory and MSD dizzy parts are no better that fomoco parts. The coils might be hotter the the fancy "billet" dizzy's and internals are all really just no better that a plain old fomoco dizzy.

Bryce

 

[.94 OR]

Any recommendations on upgrading to a FoMoCo electronic distributor? I'm running the stock '71 points and wonder about upgrading.

 

[Bronco717274]

.94 OR You can't you have to buy a whole new truck. It's not that hard just go to salvage yard and gather your part's.

 

[.94 OR]

New truck? Sheesh I drive a 2008 and will likely trade up to a 2012 this year, does that count?

 

[lman]

Ok so like I had said, after redoing the dist the truck started running well. But it has another problem now... it will run and idle fine, with plenty of power, but after about 200 yards of driving it stalls. Once I get it running again it has no power. Most of the time it will start working after reving it a few times. So it must be a fuel problem. I was thinking it might be the fuel pump. But not sure. Any ideas?